Bornavirus Antibodies Detected in Horses in Iceland

The virus' presence should not be cause for alarm among Icelandic horse owners, however, as borna antibodies are also detected in healthy horses, Björnsdóttir said.

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In a country isolated from the rest of the world, in which horse importation is strictly prohibited, local horses have tested positive for antibodies against a virus previously undetected in equids on the island: Several horses residing at a single stable in northern Iceland tested positive for borna disease virus (BDV) antibodies.

Several of the positive horses showed clinical signs of borna disease—specifically, neurologic problems, said Sigridur Björnsdóttir, DVM, PhD, study author and veterinary officer for equine health and welfare in Iceland. However, veterinarians could not conclude definitively that BDV was the source of the neurologic problems, she added, as other diseases could not be ruled out.

Borna disease is a rare and potentially fatal equine disease most commonly identified in central Europe. In the study, Björnsdóttir and colleagues explained, "The clinical signs in horses usually start with disturbances in feed intake, fever, and various degrees of somnolence. Later, ataxia (incoordination) and other gait disturbances, more severe somnolence, and finally paralysis of extremities and head develop. Other mental changes are also common, such as depression, coma, and excitations."

Researchers don't yet know the virus' transmission routes; however, previous research has suggested reservoir hosts—such as wild birds, rodents, and insectivores—are likely involved, the team noted.

In Björnsdóttir's study, researchers found that six of eight horses residing at one stable showed neurologic signs, including ataxia (incoordination). One of those four horses was euthanized due to severe neurologic deficits, she said. None of the horses tested positive for equine herpesvirus-1, West Nile virus, or the equine arteritis virus. However, four of the six affected horses were positive for BDV antibodies; one horse with neurologic signs and the euthanized horse were not tested.

One of the two healthy horses at the stable was seropositive for antibodies, and the other was seronegative, Björnsdóttir noted.

This marks the first time veterinarians have identified antibodies against BDV in horses in Iceland, she said.

A year later, a horse residing in a stable about 50 kilometers (about 31 miles) southwest of the affected stable tested positive for BDV; there was no contact between the two stables, and the affected horse, along with its three stablemates, remained healthy, Björnsdóttir said.

As BDV can be carried by a wide variety of species, Björnsdóttir said the most likely transporter in this case was birds migrating from areas where the disease is more commonly seen.

However, the presence of the virus is no cause for alarm among Icelandic horse owners, she said. “There might have been a correlation between serious sickness in a few horses in north Iceland and antibodies against the virus, but as nothing has happened since then—and as borna antibodies are also detected in healthy horses—there is no reason to believe that bornavirus presents at the moment a threat for the horse population,” Björnsdóttir told The Horse.

Because viruses such as BDV and, more importantly, Streptococcus equi (the bacteria that causes strangles) can be imported on inanimate objects, Icelandic officials ask that visiting equestrians only bring clean riding clothing and disinfected boots into the country, she said. Additionally, no used riding gloves can be brought into the country.

About the Author

Christa Lesté-Lasserre is a freelance writer based in France. A native of Dallas, Texas, Lesté-Lasserre grew up riding Quarter Horses, Appaloosas, and Shetland Ponies. She holds a master’s degree in English, specializing in creative writing, from the University of Mississippi in Oxford and earned a bachelor's in journalism and creative writing with a minor in sciences from Baylor University in Waco, Texas. She currently keeps her two Trakehners at home near Paris. Follow Lesté-Lasserre on Twitter @christalestelas.

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